Twisting process



Dec. 25, 1962 E. H. OLSON TWISTING PROCESS Filed June 30. 1959 FIG!INVENTOR EARL HERBERT OLSON ATTORNEY tent .a corporation of Delaware IFiled June 30, 1959, Ser. No. 824,025

8 Claims. (Cl. 57157) This invention relates to textured stretch yarns.More particularly, this invention has reference to the production ofsuch structures from yarns composed of synthetic polyamides, polyesters,and the like by a process which obviates the usual irnprocess twistingoperations.

Nylon filaments were the first therornplastic textile materials capableof being heat set to a degree sufiicient to permit preparation oftextured crimp and stretch yarns, for example, of the Helanca variety.Initially, such yarns were prepared in a stepwise operation during whichcontinuous multifilament yarn first was highly twisted, the twistedyarn, usually packaged, then heated to set the twist, and finally thetwist-set yarn was backtwisted to produce a structure which, upon.subsequent exposure to conditions of relaxation, would coil, curl, orspontaneously crimp into a structure exhibiting greatly enhanced built.In addition to increased bulk, such yarns would exhibit increasedelasticity. By suitable adjustment of processing conditions, yarnsexhibiting a surprisingly high degree of elasticity could be prepared.

An essential step in the production of textured stretch yarn is thatwherein a high level of twist is set in the yarn by exposure toplasticizing agents, for example, heat, steam, solvents. and/or thelike. In the stepwise or batch process, yarn first is twisted to veryhigh levels, e.g., on the order of 30 turns per inch or more withconventional twisting means, and then set in that configuration in asubsequent operation, which usually involves packaged yarn. In thecontinuous process, the yarn is subject to the action of a falsetwister, which serves to generate a segment of yarn in the runningyarnline which contains a very high level of twist. The highly twistedsegment of yarn upstream of the false twister is exposed to plasticizingconditions, permitting thereby continuous setting of the yarn in thehighly twisted configuration. Upon passing the false twister, the yarnloses the temporary false twist, yet, by virtue of the setting treatmentremembers its experience in the highly twisted state.

The most time-consuming operation in either the continuous or the batchprocedure is twisting. Mechanical up-, down-, or falsetwisters depend onrotating mechanical parts. These components severely restrict processingspeeds because of the limiting effects of friction, centrifugal force,and the like. Because of these and other limitations, presentlypracticed stretch yarn processing is a low-output time-consurningproposition. Moreover, the mechanics of those operations and theadditional handling required thereby often result in yarn of reducedquality and uniformity. All of these factors combine to render theconventional textured stretch yarn a disproportionately expensivecommodity.

An object of this invention is to provide a process and apparatus forpreparing stretch-type yarns at high speeds. A further object is toprovide an apparatus for producing stretch-type yarns, the essentialtwisting component of which is non-rotating. Another object of thisinvention is a process and apparatus whereby yarn may be colddrawn andconverted into a textured stretch yarn in a single continuous operation.A still further object is such a process wherein yarn is twisted at anetfective rate approaching one million turns per minute. These and otherobjects, together with means for accomplishing them, will appearhereinafter.

According to this invention a continuous thermoplastic synthetic organictextile strand, hereinafter referred to as a yarn although it may be asingle filament, tape, etc., is plasticized and then passed, while stillplasticized, in about one or more helical wraps about a fine wire,followed by winding the yarn (e.g., to a package) in conventionalmanner. In a preferred embodiment, a stretch yarn is prepared during aconventional drawing operation by subjecting as-drawn yarn, prior topackaging, to the essential steps of this invention. In anotherpreferred embodiment, the yarn is imparted additional twist upstreamfrom the wire by over-end take-off of the feed yarn from the supplypackage, the total level of twist up stream from the wire, i.e., in thetwist setting zone, being controlled by the wire. By this invention,there can be produced at very high speeds a yarn which, after exposureto relaxing conditions, exhibits a high and uniform level of developedtwist, twist which serves to render the resulting structure highlyelastic.

In the following description of the invention, the term latent twistrefers to that twist which has been set in the yarn by the instantprocess. Such twist usually is not apparent from the overtcharacteristics of the product, but can be developed after suilicientexposure to conditions of relaxation, e.g., by steaming or heating theyarn under conditions of minimum restraint. The term twist setting" orsimply setting refers to the two-step procedure involvingplasticization, which permits (owing to reduced torsional modulus, etc.)the yarn to assume a highly twisted configuration, followed byquenching, which fixes sufiiciently the configuration assumed by theyarn while in the plastic condition so that the yarn retains a memory"for that configuration and tends to return to it whenever distorted,unless later reset in another configuration.

The invention may be better understood by referring to the attacheddrawing, wherein:

FIGURE 1 is a schematic view of a preferred apparatus arrangement forprocessing yarn in accordance with the invention and FIGURE 2 is an endview of the hot plate 12 shown in plan view in FIGURE 1.

Referring to the drawing, there is shown an apparatus assembly wherebythis invention may be utilized to pre' pare stretch yarn immediatelyafter drawing a supply yarn, prior to packaging. According to thisembodiment, undrawn yarn 1 is removed over the end of package 2 by wayof guide means 3, then passes guide 4 onto and around cot S thence aboutdriven feed roll 6. The yarn is thereby supplied at predetermined speedby feed roll 6 to draw pin 7, takes one or more wraps thereabout thenpasses to and around draw roll 8 and its associated canted separatorroll 9. The yarn is drawn at pin 7 due to the urging of draw roll 8which, of course, has a higher peripheral speed than the speed at whichthe yarn is supplied from feed roll 6. From draw roll 8 theyarn ispassed over pin guides 10 and H and then through the slot in hot plate12, then passes in at least about one helical wrap about the fine wire13. From the wire, the yarn again encounters draw roll 8. If desired,draw roll 8 may be of stepped construction, in order to permit the yarna metered amount of relaxation while it is in the vicinity of hot plate12. From draw roll 8, the yarn passes pigtail guide 14 and is wound upin conventional manner by ring 16 and traveler 15 onto package 17 driventhrough spindle 13 1 drive means not shown).

The yarn path between the feed roll and the draw roll (initial contact)can be considered as the drawing zone." The yarn path between the drawroll and the windup can be considered as the stretch processing zone. Inthis embodiment, freshly drawn yarn passes from the draw e into thestretch processing zone. Surprisingly, as yarn passes the wire,downstream from the hot plate, s twisted by the wire. The direction ofsuch twist or 2) depends on the disposition of the wire with root to theyarn path. In general, the wire should be lted in the direction of theyarn travel in order to oh- 1 unidirectional, i.e., non-alternating,twist in the yarn. There exists a second and equally important source ofst. Since, in the preferred embodiment shown, the n is taken offover'end from the supply package 2, one 1 of twist is generated for eachconvolution of the yarn ut the supply-package. The magnitudeof such,twist )f course, of a very low order, and is further dispersed m extentproportional to the amount of drawing which as place. Such twistnormally proceeds evenly to the dup package. However, the wrap of yarnon the wire res to limit the passage of such twist, thereby causing ighyet uniform concentration of twist to accumulate ve the wire in thevicinity of the hot plate. Such twist onfined mainly in the zone betweenthe pin guides 11 and the wire 13, that is, in the vicinity of theplate. If it is desired to confine further the upstream it accumulation,more acute snubbing means should employed, e.g., meshing gears. The hotplate (or ivalent plasticizing means) functions to plasticize the ttedsegment of yarn upstream from the wire. Ob- Jsly, the twist resultingfrom over-end take-off should in the same direction as the twistgenerated by the e in order to obtain maximum benefit from each source.or being set in the highly twisted configuration, the n is efiectivelybacktwisted" after passing the wire, l can be wound up in an essentiallyuntwisted state, luding, of course, the generally low level of twistgented at the windup and that which passes the wire. The various factorswhich determine the potential reliability, i.e., the amount of latenttwist in the prodof this invention (in addition to the nature andidentity the yarn per se), include the nature, mode, and durarof theplasticizing step, the amount of quenching Ech occurs between thesetting means and the wire, the ree of compliance of the yarn about thewire, the :ction of twisting at the windup, and so on. in importantfacet of the process of this invention is step whereby the twist whichaccumulates in the sticized yarn upstream of the twisting wire i set 4he running yarn by cooling, forming thereby the latent st on which theultimate character of the product is dicated. Plasticizing may beaccomplished in a numof ways, the preferred method utilizing dry heat.table sources of heat include hot plates, radiant heatinfrared lamps,ovens, and the like. Also useful as sticizing agents are hightemperature liquid baths, pro- :d that such liquids are reasonably inerttowards the :1. Mineral oil, molten metal, or the like may be used :uchbaths. Setting may be facilitated by treating the n with mild swellingagents, such as those disclosed in I. 2,157,119 (Miles), viz.,hydroxylated non-solvents nylon. The etfectiveness of any settingtreatment ends on the degree of plasticizing achieved, i.e., by theation and efficacy of the particular treatment employed r to cooling. Ithas been determined that the most :ctive setting operation involves theuse of the highest sible plasticizing temperature which still avoidsfusion degradation of the yarn. In general, the yarn temature duringplasticization should be above the so- [ed second-order transitiontemperature but below the lting point of the polymer. Temperatures lowerthan second-order transition temperature of the yarn mate- 1 are usuallynot employed because, under these condi 15, any crimping of thefilaments is not permanent and ity of the product is reduced. Thepreferred temperae is that which results in plasticization withoutfusion degradation of the yarn. Moreover, the higher the n speed, thelonger should be the path of exposure to setting means, in order toachieve a similar effective 4 treatment. At very high yarn speeds, thetemperature of the plasticizing means may even exceed the melting pointof the yarn composition, owing to the abbreviated exposure. High denieryarn usually requires longer exposure and/or higher temperatures duringplasticizing to compensate for the greater mass of the filaments.

At high yarn speeds, high temperatures and/or longer exposure distancesare necessary to provide temperatures at the desired plasticizing level.These higher yarn temperatures may be achieved by means of an auxiliaryheating device or pre-heater in the threadline, but a simple means forachieving this same effect is to have the yarn pass twice over a singleheated plate so that yarn is preheated as it passes up along one face ofthe hot plate to a snubbing point and then is plasticized as the yarnprogresses down across the reverse face of the hot plate to the wire.

After the setting step, the yarn should be quenched to an appreciableextent prior to its encountering the wire. As indicated hereinabove andunderstood in the art, quenching is the process step whereby the yarn isfixed in the highly twisted state it assumed while plastic. The greaterthe extent of quenching, the greater the amount of latent twist which isset in the yarn. Quenching may be accomplished by rapidly cooling of thefilaments, removal of plasticizing or swelling agents, or the like,whichever is applicable. On the other hand, it is preferred thatquenching not be completed until the yarn has passed the wire.Otherwise, the yarn assumes a rod-like character, i.e., a stifinesswhich can detract from its compliance at the wire. This, in turn,reduces the total level of twist in the yarn. Accordingly, the quenchingstep should be a compromise on the basis of the twist level desired inthe product. The optimum amount of quenching can be determined byroutine experimentation.

In its simplest embodiment, the apparatus of this invention comprises inserial relationship, yarn forwarding means, plasticizing means, theangularly disposed wire or its equivalent, and yarn takeup means. Theyarn forwarding means are conveniently driven rolls or the like wherebyyarn can be forwarded from a previous processing step or supplied from apackage at predetermined speed to the twist setting means. The twistsetting means, as discussed hereinabove, may be a hot plate, a hot bath,or the like, suitably disposed along the yarn path so as to provideadequate exposure of the yarn to the plasticizing conditions. The wire,about which the yarn makes at least about one helical wrap, is located apredetermined distance along the yarn path from the setting means, inorder to allow the optimum amount of quenching of the plasticized yarn.The wire ordinarily makes an angle of between about 30 to about 60 tothe yarn path. The single helical wrap of the yarn seems to be optimumfor the purposes of this invention; very little additional benefitderives from increasing the an. ber of wraps. However, twisting startsto iaii oi the wrap is reduced to substantially less than u Preferably,the diameter of the wire is as smali as is practical. Experimentalresults indicate that the amount of twist obtainable depends in aninverse manner upon the diameter of the wire; Wire of a diameter ofabout 0.003 inch or less is preferred for the practice of thisinvention.

The yarn takeup means may be any of the conventional windup assemblies,including an uptwister, downtwister, or reciprocating traverse windup.Alternatively, the takeup means merely may forward the yarn to asubsequent operation or process step without an intervening packagingstep. In the case where the takeup means is a twisting windup, thedirection of twist imparted to the yarn at the windup should be in thesame direction as that being developed upstream from the wire.Otherwise, the existence of opposite-hand twist immediately downstreamfrom the wire may detract from its value both as a twist generator andas a twist valve.

s a es? In most of the above apparatus assemblies, yarn stringup is mostsimply accomplished by passing the wire about the yarn, then tauteningthe wire which results in the yarn being wrapped around the wire. Theabove assemblies, with relatively straight-forward modification, can 5be utilized in multiple-end applications, including those whereby two ormore yarns are imparted opposite-hand latent twist and plied at thewindup to form balancedtwist products.

The process of this invention is relatively insensitive to yarn tensionor speed. This behavior is quite unlike thatof the prior art processes,where very low yarn speeds are required and tensions of a low order arenecessary to permit eflicient twisting. The instant process may be Ioperated with or without relaxation, based on relative 5 yam lengths, inthe setting zone. By operating at relatively high tensions in thesetting zone, yarn tenacities and moduli are not diminished in thatstep, as is the case with inert prior art procedures. Therefore, in mostprocedures or operations carried out in accordance with this invention,yarn is processed without overfeed into the setting zone. In general,this invention is applicable to yarns composed of thermoplasticmaterials capable of being twist-set by plasticization and quenching. Itis particularly applicable to yarn or the like structures composedeither partially or entirely of synthetic polymeric materials such asthe polyamides (nylon), e.g., poly(ecaproamide) and poly(hexamethyleneadipamide); polyesters, e.g., poly(ethylene terephthalate),poly(trans-phexahydroxylylene terephthalate); vinyl polymers, e.g.,poly(vinyl chloride), poly(vinylidene chloride); the numerous copolymersof the above compositions; cellulose triacetate, and the like. Theseyarns may contain any of the conventional yarn additives, such asdelusterants, pigments, and the like. Where heat is employed as tions ofrelaxation. The developed twist" (t.p.i.), which includes both twist dueto inherent yarn liveliness and latent twist which develops uponsteaming, was determined by steaming (atmospheric steam) the yarn whileunder a tension of 0.0012 gram per denier. The tension was applied byfastening a piece of aluminum foil at the free end of a suspendedmeasured length of yarn. A beam of light was directed so that itsreflection from the foil would illume a photocell, twice per eachcomplete revolution of the test yarn. An electronic counter suitablyconnected to the photocell counted the number of revolutions made by theyarn during the steaming step, enabling the determination of the extentof twist development during such steaming. Results are expressed on aturns-per-inch basis. Even though the foil rotated quite rapidly duringsteaming, often in excess of 100 r.p.rn. this method gave entirelyaccurate results. The results show the affect or" varying importantprocess and yarn conditions on the amount of developed twist in theproduct.

The apparatus employed in all of the examples is shown diagrammaticallyin FIGURE 1. The draw pin, composed-of Alsimag," is 1 inch in diameter,and the yarn makes one wrap (360) thereabout. The draw roll is ofpolished chrome, 2 inches in diameter. The hot plate is made ofaluminum, extends 10 inches along the yarn path, and contains a width xdepth slot in which the yarn runs during processing. The hot plate iselectrically heated; thetemperature is controlled by the amount ofcurrent to the plate. The wire is composed of high tensile steel and hasthe diameters indicated in Table I. The process speed reported is basedon the yarn speed, in yards per minute, in the stretch processing zone.The wire is located 2 inches from the hot plate, at an angle of 45 tothe yarn line.

Table I Yarn, as-drawn Filament Draw Processing Hot late Wire Devolo edRun count (den/til.) cross section ratio speed ter! 1 p., diameter,twist (y.p.rn.) C. in (t.p.i.)

15/1 nylon l Round 4. 54 424 250 0. 003 11-15 -do--- 4. 47 424 250 0.00320-25 d0- 4. 41 424 250 0. 003 38-40 15/2 nylon 1 3. 88 424.- 250 0. 00382-4-1 15/5 nylon L 3. 17 424 250 0. 003 18-20 20 7 nylon l 3. 17 424250 0. 003 15-lS 30/10 nylon 1 3. 17 424 250 0. 003 14-18 30/4 nylon l3. 88 4.24 260 0. 003 25-27 /14 nylon 3. 17 424 250 0.003 S-l0 /0 nylon3. 83 424 250 0. 003 10-17 15/2 nylon -.---d0. 3. B8 780 250 0. 00320455 15/l-nylon 1 Cruetiorm 4. 47 780 250 0. 003 18-24 15/2polytethylene Round 3. 12 424 225 0. 005 20. 33

terephthalatc) 1 Poly(hexarnethylone adipamide) the setting agent, it isdesirable that the yarn contain a r suitable antioxidant. Suitableantioxidants for nylon are d disclosed by Stamatoff in US. Patents2,705,227; 2,640,044; and 2,630,421. Other useful antioxidants aredisclosed by Gray in US. Patent 2,510,777, and Dreyfus in US. Patent2,345,700.

It has been found that by the instant process, the highest level oflatent twist can be set in yarn which is freshly drawn, as compared withaged or lagged yarn. Also, highest levels of latent twist result whenthe yarn being processed has other than circular cross sectionfilaments, e.g., yarns of filaments having ribbon, cruciform, or the 60similar non-round cross sections. It is believed that such yarns aremore compliant in the wrap about the twisting wire. Finally, the levelof latent twist usually increases as the total denier of the yarn isdecreased, at constant denier-per-filament, or as the number offilaments is decreased, at constant total denier.

The following examples illustrate various embodiments of the process ofthis invention. The results, listed in Table I, are reported on thebasis of the amount of twist which develops in the product duringcontrolled condi- It is apparent from inspection of Table i that quitehigh levels of latent twist can be imparted at hi' h i a running yarn.In experiment ll, for ex receives up to about 980,000 turns of d perminute. The various factors Cfiflilib amount of latent twist areapparent from ins--- the table and from the discussion hereinabove. Forbest results, the relaxing conditions employed to develop latent twistapproximate the original plasticizing conditions. Where heat is used,the yarn temperature during plasticizing and subsequent relaxing shouldbe above the secondorder transistion temperature of the yarn but belowthe melting point of the yarn.

The process of this invention can he carried out at any practicalyarn-processing speed during any convenient stage of yarn handling, butit is preferably carried out during the drawing operation. Yarn tensionduring stretch processing need not be maintained at any extremely highor low level in order to insure opcrability, rather it should berelatively constant when product uniformity is desired. The product doesnot incur a tenacity loss during stretch processing in accordance withthis invention. The ap assess! us of this invention is compact andinexpensive, and res little or no maintenance due to the absence of mgor rotating parts. The stretch product is fully alent in performance tothe comparable yarns prel via the cumbersome and expensive prior artproce- The many other advantages inherent in the pracaf this inventionwill be readily apparent to those rtaking its practice.

18 claimed invention:

In the process for producing stretch yarn wherein a ling yarn ofthermoplastic organic polymer filaments tsticized by heating to atemperature below the melttoint during passage through a heating zone,is subsetly deplasticized by cooling during passage through a lag zone,is twist-set during passage through said heatand cooling zones byapplication of a false twist to up twist into the heating zone and thenremove the ied false twist after a high level of latent twist has me setin the cooling zone, and the twist-set yarn is ad into a package, theimprovement of applying said t by passing the yarn, in said cooling zonewhile still tally plasticized, in at least about one 360 helical arounda fine stationary wire positioned slarttwise ss the yarns path at anangle thereto in the range of it 30 to about 60 to accomplish a falsetwisting :t and thereby cause twist to be built up in the heating Theprocess of claim 1 in which the yarn being processed is "as drawn" yarnwhich has been freshly drawn but not packaged.

3. The process of claim 1 in which the yarn being processed is removedfrom a supply package by over-end take-off.

4. The process of claim 1 in which the yarn is poly (hexamethyleneadipamide).

5. The process of claim 1 in which the wire is round and has a diameterof less than about 0.003 inch and lies at an angle of between 30 and 60of the yarn path.

6. The process of claim 1 in which the yarn is poly (ethyleneterephthalate).

7. The process of claim 1 in which the yarn being processed has ancut-of-round cross section.

8. The process of claim 1 in which the yarn is poly (e-CZPIO amide)References fitted in the file of this patent UNITED STATES PATENTS2,451,919 Clarkson Oct. 19, 1948 2,875,502 Matthews et al Mar. 3, 19592,919,534 Bolinger et al Ian. 5, 1960 2,943,433 Van Dijk luly 5, 1960FOREIGN PATENTS 200,740 Australia Feb. 9, 1956 210,620 Australia Oct. 9,1957 802,689 Great Britain Oct. 8, 1958 808,213 Great Britain Ian. 28,1959

